This invention relates in general to superheat controllers. In particular, this invention relates to an improved method and apparatus for simultaneously calibrating and/or testing pressure sensors within multiple superheat controllers.
U.S. Pat. No. 9,140,613 discloses a superheat controller (SHC). The SHC disclosed therein is a single, self-contained, stand-alone device which contains all the sensors, electronics, and intelligence to automatically detect a fluid type, such as refrigerant, and report the superheat of multiple common fluid types used in residential, industrial, and scientific applications. U.S. Pat. No. 9,140,613 is incorporated herein in its entirety.
FIGS. 5 and 6 herein illustrate a known SHC 10, which is similar to the superheat controller disclosed in U.S. Pat. No. 9,140,613. As shown in FIGS. 5 and 6, the illustrated embodiment of the SHC 10 includes a housing 12 having a body 14, a cover 16, and a fluid inlet member 18. The fluid inlet member 18 may be secured to the housing 12 by a mounting ring 19. The mounting ring 19 attaches the fluid inlet member 18 to the housing 12 portion by a threaded connection. Alternatively, the mounting ring 19 may be attached to the fluid inlet member 18 by any desired method, such as by welding or press fitting. In the embodiment illustrated in FIGS. 5 and 6, the fluid inlet member 18 is a brass fitting having a centrally formed opening that defines a sealing surface 20. When used in a known manner in a conventional heating, ventilating, air conditioning, and refrigeration (HVAC-R) system (not shown), the sealing surface 20 of the SHC 10 may engage a connector in the HVAC-R system to define a metal to metal seal.
Known superheat controllers include a pressure sensor as an integral component thereof. For example, the known SHC 10 includes an integrated pressure and temperature sensor 22 having pressure sensor portion 24 and a temperature sensor portion 26 mounted to a printed circuit board (PCB) 28. A superheat processor 30, a data-reporting or communication module 32, and an Input/Output (IO) module 34 are also mounted to the PCB 28. The IO module 34 is a physical hardware interface that accepts input power and reports data through available hard-wired interfaces, such as wires or cables 36, to the superheat processor 30. Target devices that may be connected to the SHC 10 via the IO module 34 are schematically illustrated at 38 in FIG. 6 and may include additional temperature sensors, laptop and notebook computers, cell phones, memory cards, and any device used in or with conventional end of the line test equipment. Alternatively, the target devices 38 may be connected to the communication module 32 by a wireless connection.
The superheat processor 30 is mounted to the PCB 28 and is a high-resolution, high accuracy device that processes the input signals from the pressure and temperature sensor portions 24 and 26, respectively, of the integrated pressure and temperature sensor 22, detects the fluid type, calculates the superheat of the fluid, and provides an output that identifies the level of the calculated superheat. The superheat processor 30 may also be configured to provide other data, such as fluid temperature, fluid pressure, fluid type, relevant historical dates maintained in an onboard memory (such as alarm and on-off history), and other desired information. Advantageously, the superheat processor 30 maintains a high level of accuracy over a typical operating range of pressure and temperature after a one-time calibration. Non-limiting examples of suitable superheat processors include microcontrollers, Field Programmable Gate Arrays (FPGAs), and Application Specific Integrated Circuits (ASICs) with embedded and/or off-board memory and peripherals.
In the known SHC 10, a pressure sensor or transducer, such as the pressure sensor portion 24, may be supplied in a non-calibrated condition, and thus the SHC 10 must be calibrated, such as within a conventional environmental chamber. A known calibration sequence for the SHC 10 requires that the SHC 10 be stabilized two different temperatures. At each of the two temperatures, the calibration sequence must be completed and stored at two different pressures. After the calibration is completed at the two pressures at each of the two temperatures, the SHC 10 is returned to a verification temperature, typically room temperature, and the accuracy of the calibration is verified at a plurality of pressure points, such as five pressure points.
Typically, the time required to stabilize the SHC 10 at each of the two calibration temperatures and at the verification temperature is about one and one half hours (1.5 hrs). Although the time required to stabilize the SHC 10 at each of the two calibration temperatures and at the verification temperature will vary with the type and characteristics of the environmental chamber used, the time may be within the range of about 1.0 hours to about 2.0 hours. The time required to perform the calibration sequence and to store the results in the SHC 10 may be about 10 minutes. Thus, most of the time required for calibration and verification is spent in reaching and stabilizing the SHC 10 at the two calibration temperatures and at the verification temperature. For example, the time required to individually calibrate and verify 25 SHCs 10 in a known manner is approximately 79 hours.
Thus, it would be desirable to provide an improved method and apparatus for simultaneously calibrating pressure sensors within multiple superheat controllers.